1. Field of the Invention
The present invention relates generally to implantable, radially expandable medical devices for occluding fluid flow in a body lumen. In particular, the present invention is an occlusion device having an interwoven support structure and fluid flow-occluding membrane.
2. Description of the Related Art
Medical devices adapted for implantation in body lumens that support fluid flow are well known and commercially available. One such device is the self-expandable stent of the type disclosed in the Wallsten U.S. Pat. No. 4,655,771, which is expressly incorporated herein by reference in its entirety. Self-expanding stents can be used to treat vascular stenosis and to maintain openings in the urinary, biliary, esophageal, tracheal and bronchial tracts of a patient. Self-expanding stents of the type shown in the Wallsten patent are formed from a number of resilient filaments that are helically wound and interwoven to form a porous lattice. The stents assume a substantially tubular form in their unloaded or expanded state when they are not subjected to external forces. When subjected to inwardly-directed radial forces, the stents are forced into a reduced-radius and extended length form, known as the loaded or compressed state. A delivery device, such as a catheter, that retains the stent in its compressed state is used to deliver the stent to a treatment site through a lumen in a patient's body. After the stent is positioned at the treatment site, the delivery device is actuated to release the stent, thereby allowing the stent to self-expand and engage the body lumen. The delivery device is then detached from the stent and removed from the body.
Another type of implantable device is a vena cava filter. Vena cava filters are implanted in the vena cava that lead to a patient's heart in order to trap emboli in the fluid flow that would otherwise be carried into the heart and lungs. Vena cava filters can include a structure similar to the self-expanding stents described above, but act as a filter that traps large particles and emboli in the flow while allowing the remaining fluid flow to pass through the device.
It is sometimes desirable, however, to completely occlude a body lumen or stop fluid flow to a lumen that has been bypassed. By way of example, occlusion can be used to control internal bleeding, bypass a lumen, relieve the pressure created by an aneurysm in a lumen, or stop the flow of fluid to a tumor in a lumen. Because of their generally porous nature and substantially tubular expanded form, self-expanding stents are typically not used to occlude a fluid flow within a body lumen. Similarly, vena cava filters are specifically designed to filter and trap only emboli while allowing the remaining fluid flow in a lumen to pass through the filter, and thus are not typically used to occlude a lumen.
Implantable medical devices have been designed, however, to occlude fluid flow in a body lumen. One such device is a balloon that is carried to a treatment site by a catheter or other similar instrument. When positioned at the treatment site, the balloon is filled with a fluid, such as a polymerized resin, thereby occluding the fluid flow in the body lumen.
Another type of implantable occlusion device is a wire coil that is first linearly stretched and then positioned at a treatment site in the body lumen. Devices of this type are generally disclosed in the Ritchart et al. U.S. Pat. No. 4,994,069 and the Phelps et al. U.S. Pat. No. 5,522,822. The coil is delivered to a treatment site by a catheter. Upon being released from the catheter the coil assumes a randomly shaped mass that substantially fills the lumen. The coil can also be coated with fibers or a braided fibrous element to promote clotting of the fluid flow at the treatment site.
A continuing need exists, however, for implantable medical devices that will effectively occlude fluid flow in a body lumen. Occlusion devices exhibiting a relatively high degree of biocompatibility, that are efficient to manufacture, and that can be deployed using known techniques would be especially desirable.